Previous work on this project established a feedback effect of gonadal hormones on the cholinergic activity of the n. tractus diagonalis (td) and the ventral tegmental area (avt) of the rat brain, concomitant with hormone-induced alterations in luteinizing hormone (LH) secretion. The present work suggests that a) the changes in cholinergic activity are secondary to the alterations in LH secretion, rather than causative; b) the changes may in fact result from hormone-induced alterations in pituitary trophic hormone secretion, since hypophysectomy prevents them; c) the observed changes in cholinergic activity are a physiological manifestation of a neuroanatomical link between the mesolimbic dopamine (DA) system originating in the avt and the cholinergic system originating in the td.